Selective code receiver



May 12, 1936. HEY 2,040,691

SELECTIVE CODE RECEIVER Original Filed May 17, 1929 Inuan ur' gnu, ELHErsZ-zEg HIT 5r."

Patented May 12, 1936 UNITED STATES PATENT OFFICE mesne assignments,

ted Electric Laboratories, Inc., Chicago, Ill., a corporation of Delaware Original application May 17, 1929, Serial No. 383,875, now Patent No. 1,988,078, dated July 81, 1934. Divided and this application February 23, 1934, Serial No. 712,551

4Claims.

The present application is a division of my prior application, Serial No. 363,875, filed May 1'1, 1929, Patent No. 1,968,078, dated July 31, 1934. The particular feature 01' the selective code receiver which is being divided out and claimed in this application relates to a system of control relays which discriminate between the dots and dashes of a received signal.

A complete understanding oi the invention may best be had from the following detailed explanation when read in connection with the accompanying drawing, comprising one figure only, which shows by means of the usual schematic diagram the complete circuit of the SOS receiver.

The wireless receiving set has been indicated at RS and not shown in detail, as these receivers are well known in the art. The receiver is arranged to be used with any oi. these sets having a plate circuit suitable for operating the plate relay P.

This plate relay may be adjusted to operate with the particular set to be used. The minor switch M is the standard ten-point minor switch well known in automatic telephony.

As is well known in the art, a complete 808 signal is transmitted as one letter, and the operation of the receiver depends upon the correct transmission of the signal in accordance with this practice. A distinct pause such as is used to separate the letters of a word in telegraphy will allow the receiver to release. However, the dashes of the signal may be made as long as desired by the operator transmitting the signal without interiering with the operation of the receiver in any way.

The complete operation 01' the receiver upon the receipt of an SOS signal of three dots, three dashes, and three dots will first be explained. The first dot of the signal is received by the receiving apparatus RS, which in turn momen- 4n tarily operates plate relay P. At its make contact 9, relay P closes an obvious circuit for relays 2 and 3 in multiple. Relay 3 is slow to operate and is adjusted to respond to the dash impulses oi the signal but will not respond to the dot impulses. Relay-2 operates and at contact it closes an obvious circuit for relay i which is made slow to'release and is adjusted to remain operated during the complete signal, provided the entire signal is received as a single letter. Relay 2 also closes a circuit from ground, contact i I, resistance l2, winding of relay 4, back contact it of relay 9, resistance i4, to battery. Relay 4 operates but is quickly released due to the opening or contact ii of relay 2 which is deenergized at the end of the dot impulse by the release 01 the plate relay. P. Before relay 4 releases, however, it closes a circuit from battery, resistance l4, back contact I8 01' relay 2, winding of relay 4, resistance i2, contact i8, resistance i8, winding of relay 8, to ground. Relay 5 operates in this circuit after relay 2 releases to remove at its armature' ii the shunt around relay 8 and at contact ll short circuits the winding of relay 4.

The operation of relay 8 also closes a circuit from ground, make contact i8 of relay 9, conductor 99, back contact i8 of relay 2i oi dot group #1, winding of relay 29, to battery. Relay 28 operates and at contact 48 closes a circuit from battery, winding of relay 20, contact 49, winding of relay 2|, back contact I8 of relay 8, back contact 82 of relay 28, back contact 11 of relay 8, back contact 88 of relay 22, make contact 88 of relay i, to ground. when relay 9 releases due to the opening of contact i5, ground shunt is removed from the winding oi relay 2i, allowing it to operate in, series with relay 29 in the abovetraced circuit. At contact 4| the impulsing lead 98 is extended to relay 22 01' dot group #2.

When the second dot oi! the SOS signal is received by the receiving set R8, relay P is again momentarily energized and in turn causes the momentary energization of relays 2, 4, and 5 in the above-described manner. The closing of contacts l8 of relay 8 completes a circuit from ground, contact i8, impulse lead 95, contact 4i of relay 2i, contact 43 of relay 22, winding of relay 22, to battery. Relay 22 operates and at contacts 42 closes a circuit from battery, winding of relay 22, contact 42, winding oi! relay 22, to ground at contact 88 of relay i over the same path as heretoiore traced for the operation of relay 2i. Upon the release of relay 8, relay 23 operates and at contacts 44 extends the impulsing lead to relay 24 of dot group #3.

The third dot of the SOS signal is received in the same manner as described for the first and second dots. In this case relays 24 and 25 of dot group #3 are operated. At its contact 41 relay 28 transfers the impulsing lead 95 to relay 22 of dot group #4. At contact 59 it closes a locking circuit for the relays oi. the first three dot groups independent of contact 82 of relay 28. This locking circuit extends from ground, contact 88 of relay i, back contact 58 of relay 22, back contact 11 of relay 8, contact 59 of relay 25, to the windings of relays 28, 29, and 2i in multiple. The first three dots of the SOS signal have now been received and registered.

When thefirstdashofthe signalisnextreceived, relay P again operates and in this case remains operated a sumcient length of time to operate relay 3 in multiple with relay B. At its back contact l3, relay 3 opens the circuit of relays I and I to prevent the operation of these relays and the registering of another dot at thistime. At contact I! relay 3 closes a circuit from ground. contact I3, conductor 33,- back contact 33 of relay 21, winding of relay 23, to battery. Relay 23 operates and at contact 33 closes a circuit from battery, winding of relay 23, contact 33, winding of relay 21, back contact 13 of relay 3, contact 33 of relay i, to ground. At the end of the dash impulse, relay 3 releases due to the opening of contact 3 of relay P and at contact l3 removes the ground shunt from relay 21, allowing it to operate in series with relay 23 in the above-traced circuit. At contact II relay 2! extends the impuising lead- 33 to relay 23 of dash group #2. The second dash of the signal operates relays 23 and 23 of dash group #2 in the same manner as described above for the operation of relays 2I and 21. Relay 23, at its contact I3, extends the impulsing lead 33 to relay 33 of dash roup #3. v

When the third dash of the signal is received, relays P and 3 operate as heretofore described. Relay 3 now closes a circuit from ground, contact I3. conductor 33, contact II of relay 21, contact 33 of relay 23, back contact ll of relay 3|, winding of relay 33, to battery. Relay 33 operates and at contact 13 prepares a circuit for relay 1 as will be described later. At contact 33 a circuit is closed from battery, winding of relay 33, contact 33, winding of relay 3|, back contact 13 of relay 3, contact 33 of relay I, to ground. When ground is removed from the impulsing lead 33 due to the release of relay 3 at the end of the dash impulse, relay 3! operates in series with relay 33 in the above-traced circuit. At contact I2 the impulsing lead 33 is extended to relay 33 of dash group #4. The function of relays 33 and 33 of dash group #4 will be explained later. At contact II relay 3| closes a locking circuit for the relays of the first three dot groups independent of contact 53 of relay 32 of dot group #4. This locking circuit extends from ground, contact 33 of relay I, contact 60 of relay 25, contact II of relay 31, contact 13 of relay 3, to the windings of relays 2|, 23, and 25 in multiple. The first three dots and the three dashes of the SOS signal have now been received and registered.

When the fourth dot of the SOS signal is next received, relay P operates and in turn operates relays 2, 3, and I in the manner already described for the first three dots. The operation of relay I closes a circuit from ground, contact l3, impulse lead 35, contact 3|, contact 33, contact 31, back contact 39 of relay 33, winding of relay 32, to battery. Relay 32 operates and at contact 33 closes a circuit from battery, winding of relay 32,

contact 33, winding of relay 33, contact 33 of relay l, to ground. The opening of contacts I3 at this time is withoutefiect as a substitute locking circuit for the relays of the first three dot groups has been closed at contacts 63 and II. When ground is removed from impulse lead II at the end of the dot impulse, relay 33 operates in series with relay 32 in the above-traced circuit. At contact III the impulse lead 35 is extended to relay 33 of dot group #5. When the next dot of the signal is received, relays 33 and 33 of dot group are operated in the same manner as relays 32 and 33 of dot group #4. The opera tion of relay 35 extends the impulsing lead 35 to relay II of dot group #6.

When the last dot of the SOS signal is received, relays P, 2, 3, and I operate in the same manner as heretofore described. The operation of relay I closes a circuit from ground, contact l3, impulse lead II, contact I of relay 2|, contact 33 of relay 23, contact 31 of relay 23, contact I3 of relay 33, contact I3 of relay 33, back contact II of relay 3!, winding of relay 33, to battery. Relay 33 operates and closes a circuit from battery, winding of relay 33, contact 33, winding of relay 3'l, contact 33 of relay I, to ground. When ground is removed from the impulse lead II due to the deenergization of relay I at the end of the dot impulse, relay 31 operates in series with relay 33 in the above-traced circuit. At contact I! it closes a circuit from ground, contact 33 of relay I, contact 13 of relay 33, contact 51 of relay 31, contact 33 of relay 3, winding of relay I, to battery. Relay I operates and at contact 3| closes an obvious circuit for the stepping magnet "of the minor switch M. Magnet 33 operates and moves wiper 33 to the first bank contact 33. This closes a circuit from ground, wiper 33, bank contact 33, alarm lamp 33, to battery, lighting the lamp to indicate that an SOS signal has been received. The pause following the transmission of the complete 808 signal allows relay I to release and open its contact 33, thereby removing ground from the holding leads, and allowing all the relays of the receiver to restore to normal.

It will be appreciated that there is a remote possibility of impulses due to static being received in combination with telegraph signals in the proper sequence and number to operate the chain of the registering relays. In view of this possibility, the first three bank contacts of the minor switch M are connected only to a lamp 30. Thus the first three signals received will bring in only a visual alarm. The remaining bank contacts, I to It, inclusive, are wired to a lamp II and also to a bell 32. Allowance is thereby made for a maximum of three possible false alarms during the time that the operator is on duty. Should an SOS call be received during this period, the minor switch M will be stepped past the fourth bank contact due to the continuous repetition of the signal. Thus an audible alarm will be sounded calling the operator to duty. The minor switch may be released by the operator at any time by depressing the non-locking release key 93, there by closing an obvious circuit for the release magnet 31.

The manner in which the. relay chain is automatically released should the received signal deviate at any point from the prescribed SOS signal of three dots, three dashes, and three dots will now be explained. It will first be assumed that the entire 808 signal is not transmitted as one letter, but that a pause occurs at some point between the impulses of the signal. In this case the pause will allow relay l to release, opening contact 33 and thereby removing ground from the locking circuits of the relay chain. This allows all relays to release and the receiver to restore to normal.

It will now be assumed that a dash is received before the first three dots of the signal have been registered. In this case the dash impulse operates relays 23 and 21 in the manner already de scribed. The operation of relay 23 opens contact 32, thereby removing the holding ground from those relays of the dot recording group which have already been operated. This allows the relays of the dot recording group to be released. Therelays 23 and 21 are maintained operated until the end of the signal when the usual pause will release relay i and restore the receiver to normal.

If four successive dots should be received before therfirst dash of the signal is received, the fourth dot will operate relays 82 and 88 in a manner already described. The operation of relay 82 opens contact 88, which removes the holding ground from the relays o! the first three dot groups, allowing them to release. In this case relays 22 and 88 are maintained operated until the end of the signal when the usual pause will allow relay 1 to release, thereby restoring the receiver to normal. The next possibility to be considered is that of a fourth dash being received after the first three dots and the three dashes of the signal have been registered. The receipt of the fourth dash will operate relays P and 8 in the same manner as already described for the first three dashes. The operation of relay 8 closes a circuit from ground, contact 19, contact 88 of relay 21, contact 88 of relay 28, contact 1.2 of relay 8l, winding oi. relay 88, to battery. Relay 88 operates in this circuit and at contact 18 closes a circuit from battery, winding of relay 88, contact l8, winding of relay 89, contact 80 of relay l, to ground. When ground is removed from the impulse lead 86 at the end of the dash impulse, relay 88 operates in series with relay 88 in the above-traced circuit. At contact ll, an obvious circuit is closed for the slow-to-release relay 8. Relay 8 operates and at contact I8 removes holding ground from the relays of the first three dash groups. At contacts 11 and I8 relay 8 removes holding ground from the relays of the first three dot groups and all relays oi the first three dot groups and the first three dash groups are thereby released. Relays 38 and 89 are maintained energized until the end of the signal when the usual pause allows relay l to release, thereby restoring the receiver to normal.

The only other possibility which might tend to bring in a false alarm is the receipt of a signal consisting of three dots, three dashes, and tour dots. Upon the receipt of the sixth dot, contact 51 is closed, thereby closing a circut for relay 1 as already described. However, the receipt of the seventh dot places ground on the impulse lead 95 which extends through contact ll of relay 2|, contact 44 of relay 23, contact 41 of relay 25, contact 50 of relay 33, contact 53 of relay 35, contact 88 of relay 31, winding of relay 8, to battery. As relay 1 is made slow to'operate, relay 8 is energized in this circuit and opens contact 84 before relay 1 has had time to energize. Relay 8 closes a locking circuit for itself extending from ground. contact 88 of relay I, contact 18 of relay 8, resistance 82, contact 83 of relay 8, winding of relay 8, to battery. Relay 8 remains locked in this circuit until the receiver is restored to normal by the release of relay I at the end of the signal.

If the last three dots of the signal were followed by a dash, relays 88 and 88 would be operated as previously explained. Relay 89 at contact 18 closes the circuit for relay 6 which operates and at contacts I6 and 18 opens the holding circuits of the relay oi the first three dot groups and the first three dash groups which thereupon release. Relay 30, in releasing, opens contact 18 thereby opening the circuit of relay 1 which has not had time to operate. The relays oi the last three dot groups and of the fourth dash group remain locked up until relay l releases during the abnormal pause between signals.

From the foregoing it will be seen that the only possible signal or combination of impulses which can operate the chain of registering relays to bring in an alarm is the SOS signal oi three dots,

three dashes, and three dots, transmitted as one letter. The possibility of this signal being duplicated by a combination of static and telegraph signals is very remote.

Although only a particular application of the invention has been described in the foregoing specification, it is apparent that the receiver could be arranged to respond only to some signal other than an SOS call without departing from the spirit of the invention.

Having described the invention, what is thought to be new and is desired to have protected by Letters Patent will be set forth in the appended claims.

What is claimed is:

1. An arrangement for discriminating between dot and dash signals comprising a dash relay operated only by dash signals, a second relay operated by both dot and dash signals, athird relay, a circuit for said third relay, said third relay operated by said second relay over said circuit responsive to a received signal, contacts on said third relay, a dot relay connected in series with said third relay through its contacts by the operation of the latter but shunted until said second relay releases at the termination of the received signal, said dot relay then operating in series with said third relay through its contacts, and means controlled by said dash relay for preventing the operation of said dot relay in case the received signal is a dash signal.

2. In combination, an incoming circuit over which dot and dash signals are received, an outgoing dot conductor and an outgoing dash conductor, a slow operating dash relay, a dot relay, a

first relay connected in multiple with said dash relay to said incoming circuit, a second relay, said dash relay operative responsive to dash signals but not to dot signals, means responsive to the reception of a dash signal over said incoming circult to fully energize said dash relay and said first relay, a set of contacts operated by said dash relay to close the circuit to said dash conductor, a second set of contacts on said dash relay, a set of contacts closed by said first relay to operate said second relay over a circuit via said second contacts on said dash relay before said second contacts are fully operated, contacts on said second relay operated thereby to prepare a circuit for said dot relay in series with said second relay, the contacts on said first relay shunting said dot relay to prevent the dot relay from operating and closing the dot conductor, said second dash relay contacts when fully operated by said dash relay opening the circuit to said second relay to deenergize the same, said dash relay and said first relay deenergizing after the end 01' the dash signal.

3. In combination, an incoming circuit over which dot and dash signals are received, an outgoing dot conductor and an outgoing dash conductor, a slow operating dash relay, a dot relay, a first relay connected in multiple with said dash relay to said incoming circuit, a second' relay, said dash relay fully responsive to dash signals and not to dot signals, means responsive to the reception of a dot signal over said incoming circuit to energize said dash relay and to operate said first relay, 2. set of contacts on said dash relay for closing the circuit to said dash conductor, a second set of contacts on said dash relay, both of said sets of contacts operated only when said dash relay is fully operated,con'tacts on saidfirst relay operated thereby to close the circuit of said second relay via the second set of dash relay contacts, contacts operated by said second relay to prepare the circuit to said dot relay in series with said second relay, said dot relay being shunted by the first relay contacts, said first relay deenergizing at the end or the dot signal to open its contacts and remove the shunt circuit from the dot relay and operate the dot relay in series with said second relay and the second contact set 01' said dash relay, contacts on 'said dot relay operated thereby to close the circuit or said dot conductor, and a second set of contacts operated by said dot relay to shunt said second relay and deenergize the same and at its contacts open the circuit or the dot relay. 1

mliyoperatingresponsivetoadashsignalbutnot toadotsignaLsaidfirstrelayoperatedresponsive toeitheradotoradashsignahcontactsonsald dashrelayforclosingthecircuittosaiddash conductor and contacts on said dot relay for closing the circuit of said dotconductor, a second relay, contacts operated by said first relay ior operating said second relay, contacts operated by said second relay for closing the circuit of said dot relay in series with said second relay, said dot relay shunted by said first relay contacts in'case the received signal is a dash and said dash relay is fully operated to prevent the closing or the dot conductor, a second set of contacts controlled by said dash relay for closing the circuit to and operating said dot relay in series with said second relay in case said received signal is a dot and before said dash relay fully operates, and other contacts operated by said dot relay for shunting said second relay to deenergize the same and in turn open the circuit of said dot relay.

HARRY E. HERSHEY. 

